If you cannot find Tylenol pain reliever at your local CVS store this flu season, it might be because that store is no longer stocking it.

CVS this month changed how it stocks Tylenol at its stores in the wake of manufacturing problems at the drug's maker, Johnson & Johnson, that have disrupted supplies for more than three years.

Under the new plan, CVS will try to have Tylenol in stores in each market, but will not have it in every store, spokesman Michael DeAngelis said.

The company is getting enough Tylenol to stock about half of its 7,400 U.S. stores, and it changed the stocking of Tylenol to eliminate empty spots on shelves where the medication would have been.

The move by the drugstore unit of CVS Caremark Corp, the second largest such unit in the United States, could be a sign of the difficulty J&J faces as it tries to fix quality-control problems and rebuild its Tylenol business.

Since 2009, faulty manufacturing has prompted J&J's McNeil unit to recall millions of bottles and packages of Tylenol, Benadryl, Motrin and other over-the-counter medicines.

At the same time, CVS and other retailers have been putting more emphasis on their private-label products, which cost less than brand-name products but can be more profitable for retailers.

The length of time it has taken for J&J to upgrade its factories and ramp up manufacturing of Tylenol has given consumers plenty of time to try the store brand and decide whether they want to pay more for Tylenol, Stephanie Prymas, Consumer health analyst at market data researcher Euromonitor International, said.

"That's a pretty long time for private-label to gain some credibility," Prymas said.

In 2009, before the recalls started, Tylenol had 56 percent of the U.S. market share for acetaminophen, the chemical name of Tylenol, according to Euromonitor. In 2012, that was down to 24 percent. At the same time, private-label market share has grown from 32 percent to 62 percent.

Prymas said that private-label products are more accepted now than 20 years ago, when deaths linked to cyanide-tainted capsules caused Tylenol to be pulled from store shelves. Private-label offerings are now more commonplace and trusted, she said.

"We're kind of expecting private label to hold on more tenaciously to what they have captured," Prymas said.

A visit to a CVS store on Chicago's North Side on Sunday showed no obvious signs that Tylenol extra strength pain reliever for adults had ever been on the shelves or any spaces for the medication had to be restocked. Instead, the shelves were well-stocked with the CVS brand.

DeAngelis declined to say whether the supply of Tylenol had changed in recent weeks to prompt the new distribution plan.

A spokesman for Walgreen Co, the largest U.S. drugstore chain, said that company has seen no change in its supply of Tylenol products.